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            <h1 style="display: none">TS进阶</h1>
            
            
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                <h3 id="接口与类型别名之间的区别"><a href="#接口与类型别名之间的区别" class="headerlink" title="接口与类型别名之间的区别"></a>接口与类型别名之间的区别</h3><figure class="highlight ts"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br></pre></td><td class="code"><pre><code class="hljs ts"><span class="hljs-keyword">interface</span> A&#123;<br>  <span class="hljs-attr">name</span>: <span class="hljs-built_in">string</span>;<br>  <span class="hljs-attr">age</span>: <span class="hljs-built_in">number</span><br>&#125;<br><br><span class="hljs-keyword">let</span> <span class="hljs-attr">a</span>: A = &#123;<br>  <span class="hljs-attr">name</span>: <span class="hljs-string">&quot;abc&quot;</span>,<br>  <span class="hljs-attr">age</span>: <span class="hljs-number">18</span><br>&#125;<br><br><span class="hljs-keyword">interface</span> A&#123;<br>  [<span class="hljs-attr">index</span>: <span class="hljs-built_in">number</span>]: <span class="hljs-built_in">number</span>;<br>&#125;<br><br><span class="hljs-keyword">let</span> <span class="hljs-attr">a</span>: A = [<span class="hljs-number">1</span>,<span class="hljs-number">2</span>,<span class="hljs-number">3</span>]<br><br><span class="hljs-keyword">interface</span> A &#123;<br>  (): <span class="hljs-built_in">void</span><br>&#125;<br><br><span class="hljs-keyword">let</span> <span class="hljs-attr">a</span>: A = <span class="hljs-function">() =&gt;</span> &#123;&#125;<br><br>------------------------------------------区别<br>对象类型、接口合并、接口继承、映射类型：<br>对象类型：<br><span class="hljs-keyword">type</span> A = <span class="hljs-built_in">string</span>  √<br><span class="hljs-keyword">interface</span> B <span class="hljs-built_in">string</span>  ×<br><span class="hljs-keyword">interface</span> B&#123;  √<br>  <br>&#125;<br><br>接口合并：接口支持，类型别名不支持<br><span class="hljs-keyword">interface</span> A &#123;<br>  <span class="hljs-attr">name</span>: <span class="hljs-built_in">string</span><br>&#125;<br><span class="hljs-keyword">interface</span> A &#123;<br>  <span class="hljs-attr">age</span>: <span class="hljs-built_in">number</span><br>&#125;<br><span class="hljs-keyword">let</span> <span class="hljs-attr">a</span>: A =&#123;  <span class="hljs-comment">// 必须同时满足两个接口A</span><br>  <span class="hljs-attr">name</span>:<span class="hljs-string">&quot;tom&quot;</span>,<br>  <span class="hljs-attr">age</span>:<span class="hljs-number">18</span><br>&#125;<br><br>接口继承：接口支持，类型别名不支持<br><span class="hljs-keyword">interface</span> A &#123;<br>  <span class="hljs-attr">name</span>: <span class="hljs-built_in">string</span><br>&#125;<br><br><span class="hljs-keyword">interface</span> B <span class="hljs-keyword">extends</span> A&#123;<br>  <span class="hljs-attr">age</span>:<span class="hljs-built_in">number</span><br>&#125;<br><span class="hljs-keyword">let</span> <span class="hljs-attr">b</span>: B = &#123;<br>  <span class="hljs-attr">name</span>: <span class="hljs-string">&quot;tom&quot;</span>,<br>  <span class="hljs-attr">age</span>: <span class="hljs-number">18</span><br>&#125;<br><br>映射类型: 类型别名支持，接口不支持<br><span class="hljs-keyword">type</span> A = &#123;<br>  [P <span class="hljs-keyword">in</span> <span class="hljs-string">&quot;name&quot;</span>|<span class="hljs-string">&quot;age&quot;</span>]: <span class="hljs-built_in">string</span><br>&#125;<br><br></code></pre></td></tr></table></figure>

<hr>
<h3 id="字面量类型和-keyof-关键字"><a href="#字面量类型和-keyof-关键字" class="headerlink" title="字面量类型和 keyof 关键字"></a>字面量类型和 keyof 关键字</h3><figure class="highlight ts"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br></pre></td><td class="code"><pre><code class="hljs ts">字面量类型：字面量作为一种类型<br><span class="hljs-keyword">type</span> A = <span class="hljs-number">1</span>  <span class="hljs-comment">// 将1作为类型存储起来，此时这个1就可以看作是一种类型</span><br><span class="hljs-keyword">let</span> <span class="hljs-attr">a</span>: A = <span class="hljs-number">1</span> <span class="hljs-comment">// 只能等于1</span><br><br>keyof：将key取出来做成联合注解<br><span class="hljs-keyword">interface</span> A &#123;<br>  <span class="hljs-attr">name</span>: <span class="hljs-built_in">string</span>,<br>  <span class="hljs-attr">age</span>: <span class="hljs-number">18</span><br>&#125;<br><span class="hljs-comment">// keyof A -&gt; &quot;name&quot;|&quot;age&quot;</span><br><span class="hljs-keyword">let</span> a = keyof A <span class="hljs-comment">// a --&gt; &quot;name&quot;|&quot;age&quot;</span><br><br><span class="hljs-keyword">let</span> a = <span class="hljs-string">&quot;tom&quot;</span><br><span class="hljs-keyword">typeof</span> a <span class="hljs-comment">// string</span><br><span class="hljs-keyword">type</span> A = <span class="hljs-keyword">typeof</span> a <span class="hljs-comment">// A - string</span><br><br><br></code></pre></td></tr></table></figure>

<hr>
<h3 id="类型保护、自定义类型保护"><a href="#类型保护、自定义类型保护" class="headerlink" title="类型保护、自定义类型保护"></a>类型保护、自定义类型保护</h3><p>类型保护允许你使用更小范围的对象类型</p>
<p>typeof、instanceof、in、字面量：</p>
<figure class="highlight ts"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br></pre></td><td class="code"><pre><code class="hljs ts"><span class="hljs-attr">typeof</span>:<br><span class="hljs-keyword">function</span> <span class="hljs-title function_">foo</span>(<span class="hljs-params">n: <span class="hljs-built_in">string</span>|<span class="hljs-built_in">number</span></span>)&#123;<br>  <span class="hljs-keyword">if</span>(<span class="hljs-keyword">typeof</span> n === <span class="hljs-string">&quot;string&quot;</span>)&#123;<br>    n.<span class="hljs-property">length</span><br>  &#125;<br>&#125;<br><br><span class="hljs-attr">instanceof</span>:<br><span class="hljs-keyword">class</span> <span class="hljs-title class_">Foo</span>&#123;<br>  name = <span class="hljs-string">&quot;tom&quot;</span><br>&#125;<br><span class="hljs-keyword">class</span> <span class="hljs-title class_">Bar</span>&#123;<br>age = <span class="hljs-number">18</span><br>&#125;<br><span class="hljs-keyword">function</span> <span class="hljs-title function_">Fn</span>(<span class="hljs-params">n: Foo|Bar</span>)&#123; <span class="hljs-comment">//现在的n 就是Foo与Bar的实例 所以直接调用Foo与Bar上的属性</span><br>  <span class="hljs-keyword">if</span>(n <span class="hljs-keyword">instanceof</span> <span class="hljs-title class_">Foo</span>)&#123;<br>    n.<span class="hljs-property">name</span><br>  &#125;<br>&#125;<br><br><span class="hljs-attr">in</span>:<br><span class="hljs-keyword">function</span> <span class="hljs-title function_">foo</span>(<span class="hljs-params">n: &#123;name:<span class="hljs-built_in">string</span>&#125; | &#123;age:num&#125;</span>)&#123;<br>  <span class="hljs-keyword">if</span>(<span class="hljs-string">&quot;name&quot;</span> <span class="hljs-keyword">in</span> n)&#123;<br>    n.<span class="hljs-property">name</span><br>  &#125;<br>&#125;<br><br>字面量:<br><span class="hljs-keyword">function</span> <span class="hljs-title function_">foo</span>(<span class="hljs-params">n: <span class="hljs-string">&quot;name&quot;</span>|<span class="hljs-number">123</span></span>)&#123;<br>  <span class="hljs-keyword">if</span>(n === <span class="hljs-string">&quot;name&quot;</span>)&#123;<br>    n.<span class="hljs-property">length</span><br>  &#125;<br>&#125;<br></code></pre></td></tr></table></figure>

<p>自定义类型保护:</p>
<figure class="highlight ts"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><code class="hljs ts"><span class="hljs-comment">// is类型谓词，它可以做到类型保护</span><br><span class="hljs-keyword">function</span> <span class="hljs-title function_">isString</span>(<span class="hljs-params">n: <span class="hljs-built_in">any</span></span>): n is <span class="hljs-built_in">string</span>&#123;<br>  <span class="hljs-keyword">return</span> <span class="hljs-keyword">typeof</span> n === <span class="hljs-string">&quot;string&quot;</span><br>&#125;<br><span class="hljs-keyword">function</span> <span class="hljs-title function_">foo</span>(<span class="hljs-params">n:<span class="hljs-built_in">string</span>|<span class="hljs-built_in">number</span></span>)&#123;<br>  <span class="hljs-keyword">if</span>(<span class="hljs-title function_">isString</span>(n))&#123;<br>    n.<span class="hljs-property">length</span><br>  &#125;<br>&#125;<br></code></pre></td></tr></table></figure>

<hr>
<h3 id="定义泛型和泛型的常见操作"><a href="#定义泛型和泛型的常见操作" class="headerlink" title="定义泛型和泛型的常见操作"></a>定义泛型和泛型的常见操作</h3><p>泛型：在定义函数、接口或者类的时候，未指定其参数类型，只有在运行时传入才能确定</p>
<figure class="highlight ts"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><code class="hljs ts"><span class="hljs-keyword">type</span> A&lt;T=<span class="hljs-built_in">string</span>&gt; = T  <span class="hljs-comment">// 设置string为默认值</span><br><span class="hljs-keyword">let</span> <span class="hljs-attr">a</span>: A = <span class="hljs-string">&quot;tom&quot;</span> <span class="hljs-comment">//默认值</span><br><span class="hljs-keyword">let</span> <span class="hljs-attr">b</span>: A&lt;<span class="hljs-built_in">number</span>&gt; = <span class="hljs-number">123</span><br><span class="hljs-keyword">let</span> <span class="hljs-attr">c</span>: A&lt;<span class="hljs-built_in">boolean</span>&gt; = <span class="hljs-literal">true</span><br><br><span class="hljs-keyword">type</span> <span class="hljs-title class_">MyArray</span>&lt;T&gt; = T[]<br><span class="hljs-keyword">let</span> <span class="hljs-attr">d</span>: <span class="hljs-title class_">MyArray</span>&lt;<span class="hljs-built_in">number</span>&gt; = [<span class="hljs-number">1</span>,<span class="hljs-number">2</span>,<span class="hljs-number">3</span>]<br><span class="hljs-keyword">let</span> <span class="hljs-attr">e</span>: <span class="hljs-built_in">number</span>[] = [<span class="hljs-number">1</span>,<span class="hljs-number">2</span>,<span class="hljs-number">3</span>]<br></code></pre></td></tr></table></figure>

<p>常见的泛型：</p>
<figure class="highlight ts"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br></pre></td><td class="code"><pre><code class="hljs ts">函数：<br><span class="hljs-keyword">function</span> foo&lt;T&gt;(<span class="hljs-attr">n</span>: T)&#123;&#125;<br>foo&lt;<span class="hljs-built_in">string</span>&gt;(<span class="hljs-string">&quot;tom&quot;</span>)<br><span class="hljs-title function_">foo</span>(<span class="hljs-number">123</span>) <span class="hljs-comment">// 自动类型推断</span><br><br><span class="hljs-comment">//常用：</span><br>函数与接口结合： <br><span class="hljs-keyword">interface</span> A&lt;T&gt;&#123;<br>  (n?:T):<span class="hljs-built_in">void</span><br>  <span class="hljs-keyword">default</span>?: T<br>&#125;<br><span class="hljs-keyword">let</span> <span class="hljs-attr">foo</span>:A&lt;<span class="hljs-built_in">string</span>&gt; = <span class="hljs-function">(<span class="hljs-params">n</span>) =&gt;</span> &#123;&#125;<br><br><span class="hljs-title function_">foo</span>(<span class="hljs-string">&quot;tom&quot;</span>) √<br><span class="hljs-title function_">foo</span>(<span class="hljs-number">123</span>) ×<br>foo.<span class="hljs-property">default</span> = <span class="hljs-string">&quot;hello&quot;</span> √<br><br>类中：<br><span class="hljs-keyword">class</span> <span class="hljs-title class_">Foo</span>&lt;T&gt;&#123;<br>  name!: T;<br>&#125;<br><span class="hljs-keyword">let</span> f = <span class="hljs-keyword">new</span> <span class="hljs-title class_">Foo</span>&lt;<span class="hljs-built_in">string</span>&gt;()<br>f.<span class="hljs-property">name</span> = <span class="hljs-string">&quot;hello&quot;</span><br><br>继承：<br><span class="hljs-keyword">class</span> <span class="hljs-title class_">Foo</span>&lt;T&gt;&#123;<br>  name!: T;<br>&#125;<br><span class="hljs-keyword">class</span> <span class="hljs-title class_">Bar</span> <span class="hljs-keyword">extends</span> <span class="hljs-title class_ inherited__">Foo</span>&lt;<span class="hljs-built_in">string</span>&gt;&#123;&#125;<br><span class="hljs-keyword">let</span> b = <span class="hljs-keyword">new</span> <span class="hljs-title class_">Bar</span>&lt;<span class="hljs-built_in">string</span>&gt;()<br>b.<span class="hljs-property">name</span> = <span class="hljs-string">&quot;hello&quot;</span><br></code></pre></td></tr></table></figure>

<p>泛型约束：</p>
<figure class="highlight ts"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><code class="hljs ts"><span class="hljs-keyword">type</span> A = <span class="hljs-built_in">string</span><br><span class="hljs-keyword">function</span> foo&lt;T <span class="hljs-keyword">extends</span> A&gt;(<span class="hljs-attr">n</span>: T)&#123;&#125;<br><span class="hljs-title function_">foo</span>(<span class="hljs-string">&quot;hello&quot;</span>)<br></code></pre></td></tr></table></figure>



<hr>
<h3 id="类型兼容性"><a href="#类型兼容性" class="headerlink" title="类型兼容性"></a>类型兼容性</h3><p>？？</p>
<p>确认一个类型是否能赋值给其他类型</p>
<figure class="highlight ts"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><code class="hljs ts"><span class="hljs-comment">// 同类型之间可以相互赋值</span><br><span class="hljs-keyword">let</span> <span class="hljs-attr">a</span>: <span class="hljs-built_in">number</span> = <span class="hljs-number">123</span><br><span class="hljs-keyword">let</span> <span class="hljs-attr">b</span>: <span class="hljs-built_in">string</span>|<span class="hljs-built_in">number</span> = <span class="hljs-string">&quot;hello&quot;</span><br><br>b = a √<br>a = b ×<br></code></pre></td></tr></table></figure>

<hr>
<h3 id="映射类型与内置工具类型"><a href="#映射类型与内置工具类型" class="headerlink" title="映射类型与内置工具类型"></a>映射类型与内置工具类型</h3><p>将已知类型的每个属性都变为可选或者只读的</p>
<p>映射类型：</p>
<figure class="highlight ts"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><code class="hljs ts"><span class="hljs-keyword">type</span> A = &#123;<br>  <span class="hljs-attr">name</span>: <span class="hljs-built_in">string</span>;<br>  <span class="hljs-attr">age</span>: <span class="hljs-built_in">number</span><br>&#125;<br><span class="hljs-comment">// 映射类型只能用别名实现，不能用接口</span><br><span class="hljs-keyword">type</span> B&lt;T&gt; = &#123;<br>  <span class="hljs-keyword">readonly</span> [P <span class="hljs-keyword">in</span> keyof T]: T[p]<br>&#125;<br><span class="hljs-keyword">type</span> C = B&lt;A&gt;<br></code></pre></td></tr></table></figure>

<p>内置工具：ts提供好了的一些映射类型，…..</p>
<figure class="highlight ts"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><code class="hljs ts"><span class="hljs-keyword">type</span> A = &#123;<br>  <span class="hljs-attr">name</span>: <span class="hljs-built_in">string</span>;<br>  <span class="hljs-attr">age</span>: <span class="hljs-built_in">number</span>;<br>  <span class="hljs-attr">gender</span>: <span class="hljs-built_in">string</span>;<br>&#125;<br><span class="hljs-keyword">type</span> B = <span class="hljs-title class_">Readonly</span>&lt;A&gt; <span class="hljs-comment">// Readonly：只读  与上面一样</span><br><span class="hljs-keyword">type</span> C = <span class="hljs-title class_">Partial</span>&lt;A&gt; <span class="hljs-comment">// Partial：可选</span><br><span class="hljs-keyword">type</span> D = <span class="hljs-title class_">Pick</span>&lt;A, <span class="hljs-string">&quot;name&quot;</span>&gt; <span class="hljs-comment">// Pick：筛选 变为所指定的</span><br><span class="hljs-keyword">type</span> E = <span class="hljs-title class_">Record</span>&lt;<span class="hljs-string">&quot;name&quot;</span>, <span class="hljs-built_in">string</span>&gt; <span class="hljs-comment">// Record 指定第一个参数为指定类型</span><br><br></code></pre></td></tr></table></figure>

<figure class="highlight ts"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><code class="hljs ts"><span class="hljs-keyword">type</span> A = &#123;<br>  name?: <span class="hljs-built_in">string</span>;<br>  age?: <span class="hljs-built_in">number</span>;<br> &#125;<br> <br> <span class="hljs-keyword">type</span> B = <span class="hljs-title class_">Required</span>&lt;A&gt;  <span class="hljs-comment">// Required 由可选项变为必选项</span><br> <span class="hljs-keyword">type</span> C = <span class="hljs-title class_">Omit</span>&lt;A,<span class="hljs-string">&quot;name&quot;</span>&gt; <span class="hljs-comment">// 与Pick相反 将选择的排除掉</span><br> <span class="hljs-keyword">type</span> D = <span class="hljs-title class_">Exclude</span>&lt;<span class="hljs-built_in">string</span>|<span class="hljs-built_in">number</span>|<span class="hljs-built_in">boolean</span>,<span class="hljs-built_in">string</span>&gt; <span class="hljs-comment">// 在参数一中排除参数二中的内容</span><br></code></pre></td></tr></table></figure>

<hr>
<h3 id="条件类型、infer关键字"><a href="#条件类型、infer关键字" class="headerlink" title="条件类型、infer关键字"></a>条件类型、infer关键字</h3><p>条件类型：在初始状态并不直接确定具体类型，而是通过一定的类型运算得到最终的变量类型</p>
<figure class="highlight elm"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><code class="hljs elm"><span class="hljs-keyword">type</span> <span class="hljs-type">A</span> = string<br><span class="hljs-keyword">type</span> <span class="hljs-type">B</span> = number<br><br><span class="hljs-keyword">type</span> <span class="hljs-type">C</span> = <span class="hljs-type">A</span> extends <span class="hljs-type">B</span> ? &#123;&#125; : []  // <span class="hljs-type">A</span>会继承<span class="hljs-type">B</span>吗 会返回&#123;&#125; 不会返回[]<br></code></pre></td></tr></table></figure>

<figure class="highlight ts"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><code class="hljs ts"> <span class="hljs-keyword">type</span> D = <span class="hljs-title class_">Exclude</span>&lt;<span class="hljs-built_in">string</span>|<span class="hljs-built_in">number</span>|<span class="hljs-built_in">boolean</span>,<span class="hljs-built_in">string</span>&gt; <span class="hljs-comment">// 留下在参数一中排除参数二中的内容</span><br>  <span class="hljs-keyword">type</span> D = <span class="hljs-title class_">Extract</span>&lt;<span class="hljs-built_in">string</span>|<span class="hljs-built_in">number</span>|<span class="hljs-built_in">boolean</span>,<span class="hljs-built_in">string</span>&gt; <span class="hljs-comment">// 与Exclude相反 只留下参数二中的内容</span><br>  <br><span class="hljs-keyword">type</span> E = <span class="hljs-title class_">NonNullable</span>&lt;<span class="hljs-built_in">string</span>|<span class="hljs-literal">null</span>|<span class="hljs-literal">undefined</span>&gt; <span class="hljs-comment">// 排除null|undefined </span><br><br><span class="hljs-keyword">type</span> <span class="hljs-title class_">Fpp</span> = <span class="hljs-function">(<span class="hljs-params">n: <span class="hljs-built_in">number</span>, m: <span class="hljs-built_in">string</span></span>) =&gt;</span> <span class="hljs-built_in">void</span><br><span class="hljs-keyword">type</span> F = <span class="hljs-title class_">Parameters</span>&lt;<span class="hljs-title class_">Foo</span>&gt; <span class="hljs-comment">// type F = [n:number, m:string] 得到型参的元祖类型</span><br><span class="hljs-keyword">let</span> <span class="hljs-attr">a</span>: A = [<span class="hljs-number">1</span>,<span class="hljs-string">&quot;abc&quot;</span>]<br><span class="hljs-keyword">type</span> G = <span class="hljs-title class_">ReturnType</span>&lt;<span class="hljs-title class_">Foo</span>&gt; <span class="hljs-comment">// type G = void 拿到返回值的类型</span><br></code></pre></td></tr></table></figure>


                
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